Obesity, defined as a body mass index (BMI) of greater than 30, is a major health concern in the United States and other countries. Current research suggests that one in three Americans and more than 300 million people world-wide are obese. www.who.int/nut/obs.htm (last visited Dec. 13, 2005). Complications of obesity include many serious and life-threatening diseases including hypertension, diabetes, coronary artery disease, stroke, congestive heart failure, pulmonary insufficiency, multiple orthopedic problems, various cancers and a markedly decreased life expectancy. Intentional weight loss, however, can improve many of these medical complications associated with obesity.
While weight loss can improve many of the medical complications associated with obesity, its management as a health concern has proven troublesome. A variety of approaches including dietary methods, psychotherapy, behavior modification, and pharmacotherapy have failed to control the rapid growth in the incidence and severity of obesity seen in the United States. According to the Center for Disease Control, obesity contributes to about 111,909 deaths annually, just behind tobacco (435,000) and ahead of alcohol (85,000), car accidents (43,000) and guns (29,000). Mokdad et al., 291(10), JAMA 1238-1245 (2004); Flegal et al., 293(15) JAMA 1861-1867 (2005). Further, the estimated annual cost of obesity in the U.S. in 2000 was about $117 billion. Centers for Disease Control and Prevention available at http:/www.cdc.gov/nccdphp/aag/aag_dnpa.html (last visited Nov. 11, 2005).
The severity of problems associated with obesity has led to the development of several drastic surgical procedures. One such procedure physically reduces the size of the stomach so that a person cannot consume as much food as was previously possible. These stomach reduction surgeries had limited early success, but now it is known that the stomach can restretch over time, limiting the achievement of sustained weight loss in many individuals. Another drastic surgical procedure induces the malabsorption of food by reducing the absorptive surface of the gastrointestinal (GI) tract, generally via by-passing portions of the small intestine. This gastric by-pass procedure further has been combined with stomach reduction surgery. While these described surgical procedures can be effective to induce a reduction in food intake and/or overall weight loss in some, the surgical procedures are highly invasive and cause undue pain and discomfort. Further, the described procedures may result in numerous life-threatening postoperative complications. These surgical procedures are also expensive, difficult to reverse, and place a large burden on the national health care system.
Non-surgical approaches for the treatment of obesity also have been developed. For example, one non-surgical endoscopic approach to treating obesity includes the placement of a gastric balloon within the stomach. The gastric balloon fills a portion of the stomach, providing the patient with a feeling of fullness, thereby reducing food intake. Many problems are associated with the gastric balloon device, however, including poor patient tolerance and complications due to rupture and/or migration of the balloon. Further, sham-controlled studies have failed to show that implantation of a gastric balloon produces a better reduction in food intake than dieting alone. Trostler et al., 19(7) Int. J. Obes. Relat. Metab. Disord. 489-495 (1995); Geliebter et al. 15(4) Int J Obes. 259-266 (1991); Mathus-Vliegen et al., 99(2) Gastroenterol. 362-369 (1990); Lindor et al., 62(11) Mayo Clin. Proc. 992-996 (1987).
Other non-surgical devices designed to induce weight loss limit the absorption of nutrients in the small intestine by funneling food from the stomach into a tube found within the small intestine so that the food is not fully digested or absorbed within the small intestine. While this type of device may be somewhat effective at limiting the absorption of consumed food, there is still room for a variety of improvements in non-surgical devices designed to induce weight loss and/or a reduction in food intake.
An understanding of biological events that contribute to the creation of satiety signals provides an opportunity to develop “smart” nonsurgical devices that can trigger such events. The amount of food that individuals consume is largely dependent on biological signals between the gut and the brain. Specifically, hormonal signals from the gut to the brain are correlated with both the onset and cessation of food intake. While increased levels of hormones such as ghrelin, motilin and agouti-related peptide are involved in the promotion of appetite and the onset of food intake, increased levels of a number of other hormones are involved in the cessation of food intake.
Various biologic events contribute to the physiologic cessation of food intake. Generally, as a meal is consumed, the ingested food and by-products of digestion interact with an array of receptors along the GI tract to create satiety signals. Satiety signals communicate to the brain that an adequate amount of food has been consumed and that an organism should stop eating. Specifically, GI tract chemoreceptors respond to, without limitation, products of digestion (such as sugars, fatty acids, amino acids and peptides) while stretch and mechanoreceptors in the stomach and proximal small intestine respond to, without limitation, the physical presence of consumed foods. Chemoreceptors respond to the products of digestion by, without limitation, causing the release of hormones or other molecular signals. These released hormones and/or other molecular signals can stimulate nerve fibers to send satiety signals to the brain. The arrival of these signals in the brain can trigger a variety of neural pathways that can reduce food intake. The released hormones and/or other molecular signals can also travel to the brain themselves to help create signals of satiety. Stretch and mechanoreceptors generally send satiety signals to the brain through, without limitation, stimulation of nerve fibers in the periphery that signal the brain. The present invention provides methods and devices that help to reduce food intake by providing non-surgical devices that trigger the aforementioned biological events that contribute to the creation of satiety signals.